From: Peter Zijlstra <peterz@infradead.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Feng Tang <feng.tang@intel.com>, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H . Peter Anvin" <hpa@zytor.com>,
Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
linux-kernel@vger.kernel.org, alek.du@intel.com,
pasha.tatashin@oracle.com
Subject: Re: [RFC 2/2] x86, tsc: Enable clock for ealry printk timestamp
Date: Thu, 31 May 2018 17:52:10 +0200 [thread overview]
Message-ID: <20180531155210.GL12180@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180531135542.4j7w7bxsw43ydx3j@pathway.suse.cz>
On Thu, May 31, 2018 at 03:55:42PM +0200, Petr Mladek wrote:
> I wonder if we could get some cleaner integration into the timer and
> printk code.
Yes, these patches are particularly horrific..
There were some earlier patches by Pavel Tatashin, which attempted do
get things running earlier.
http://lkml.kernel.org/r/20180209211143.16215-1-pasha.tatashin@oracle.com
I'm not entirely happy with that, but I never did get around to
reviewing that last version :-( In particuarly, now that you made me
look, I dislike his patch 6 almost as much as these patches.
The idea was to get regular sched_clock() running earlier, not to botch
some early_sched_clock() into it.
Basically run calibrate_tsc() earlier (like _waaay_ earlier, it doesn't
rely on anything other than CPUID) and if you have a recent part (with
exception of SKX) you'll get a usable tsc rate (and TSC_RELIABLE) and
things will work.
If you have a dodgy part (sorry SKX), you'll just have to live with
sched_clock starting late(r).
Do not cobble things on the side, try and get the normal things running
earlier.
next prev parent reply other threads:[~2018-05-31 15:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-30 9:20 [RFC 1/2] printk: Enable platform to provide a early boot clock Feng Tang
2018-05-30 9:20 ` [RFC 2/2] x86, tsc: Enable clock for ealry printk timestamp Feng Tang
2018-05-30 13:25 ` Andy Shevchenko
2018-05-30 14:17 ` Feng Tang
2018-05-31 13:55 ` Petr Mladek
2018-05-31 15:52 ` Peter Zijlstra [this message]
2018-06-01 16:12 ` Feng Tang
2018-06-06 9:38 ` Feng Tang
2018-06-06 15:25 ` Pavel Tatashin
2018-06-07 1:34 ` Feng Tang
2018-06-13 7:29 ` Feng Tang
2018-06-01 18:05 ` Pavel Tatashin
2018-05-31 7:18 ` [RFC 1/2] printk: Enable platform to provide a early boot clock Andy Shevchenko
2018-05-31 17:22 ` Randy Dunlap
2018-05-31 18:15 ` Andy Shevchenko
2018-06-14 8:38 ` Feng Tang
2018-06-14 9:08 ` Thomas Gleixner
2018-06-14 9:55 ` Feng Tang
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